It's a good puzzle game, though difficult.
It many ways, it really is like a 2D version of the Witness. Whether that was the intention, that's what it is. So if you played The Witness, you'll know the kinds of puzzles you'll get here.
At no point are you told how to do anything. That's kind of the point. You mind sees patterns, and you come up with possible solutions. If you get it right, you make a deduction, that allows you to solve future puzzles of the same type.
As a little hint of the kind of puzzles: recreating shapes, connecting the same colour without overlap, having a particular number of connected squares, minesweeper-type rules of how many on/off squares next to it, and then combining these things in later puzzles.
Where I felt this game failed slightly was in the pacing and positioning of puzzles. You have free rein over the entire island, but I found I almost always encountered impossible-to-solve puzzles before the tutorial puzzle that should teach me the rules. So this creates a high amount of frustration, where you continually encounter puzzles that you have no possibility of solving, yet don't know that there exists a simpler puzzle somewhere that will help. The tutorial puzzles themselves will be difficult because you are learning the rules, so you don't know whether any given puzzle is solvable or not.
This was made more frustrating by the fact that some end game areas had independent immediately-solvable puzzles in them, suggesting that this is where you should be, only to encounter completely unsolveable puzzles that require knowledge of the entire game.
I particularly hated the "Gallery" area, which required interpreting paintings as if they were puzzles. I was stuck there longer than any other part of the game, because although I knew all the rules, I didn't know what the pictures were supposed to be showing, and it was very open to interpretation. Eventually, drawing pictures was the only way I solved it. But it was still easy to get it wrong by 1 square, so when my answer wasn't accepted, I realised, OK, move all of this up one square and try to solve the new puzzle that would create.
After completing the game, there is an alternate ending by finding a secret area and doing more puzzles. They take the form of recognising things in the environment and translating them into puzzle elements, and I found I had to basically use photo editing programs, because I had to put lots of different things together from multiple areas, figure out how to make it into a puzzle, and then solve the puzzle I created. This was probably my least favourite part of the game. Just wandering around previously visited areas thinking "could this piece of terrain be [puzzle element]?"
The fact I did it, suggests that I wanted to do it, so I guess the game worked as a puzzle game. I couldn't just leave it, I had to solve it.
There is actually another secret area, that there is no achievement for. It's an area you're very likely to walk past, and it requires solving very difficult puzzles from the entire game to gain access to. I loved that area. There were some really beautiful complex puzzles. Once you've learnt the rules and can combine them, it's difficult but achievable and not pretending to be anything other than a difficult puzzles to solve. I thought that was better post-game content than the alternate ending stuff that I found annoying to complete.
My mild complaints aside, I obviously liked this game because I spent a lot of time playing it and solving every puzzle. If you like difficult puzzle games in a similar style to The Witness, then you will like this.
